The movement of water is the main ecological factors that control the conditions of sea grass communities. Currents and waves have a considerable influence on the aeration, nutrient transport and stirring the water. Stirring the water acts to avoid large temperature fluctuations (Trono and Fortes, 1988). Another role of the currents is to avoid the accumulation of silt and epiphytes attached to the thallus that may hinder the growth of seaweed.
Soegiarto in Sinaga (1999) suggested that the stronger the flow of the waters, the sea grass growth will be faster due to the diffusion of nutrients into the cell thallus more and more, so that the metabolism is accelerated. Flow is a factor that should be prioritized in the choice of location, because it usually flows will affect the sedimentation in the water that will ultimately affect the light (Doty, 1973).
Some water movements that affect the growth of seaweed that is, the current flowing from the sea or from land, sea waves, tide. The movement of water, in addition serves to supply nutrients also help facilitate the seaweed to absorb nutrients, cleaning up existing, and establish the exchange of CO2 with O2 so that oxygen demand is not an issue (Indriani and Sumiarsih, 1999). Currents in coastal areas strongly influenced by the movement of the tides, wind speed, the speed of movement and transportation of fresh water waves (Hutabarat, 1988).
Currents can cause movement of water that can serve as a supplier of nutrients, it also helps facilitate the seaweed to absorb nutrients, clean the dirt, as well as establish the exchange of CO2 and O2, so the oxygen requirement is not an issue (Rosdiana, 2003).
Figure 12. The movement of water plays a role in the supply of nutrients and oxygen dissolved
According Sidjabat (1973) the process of the exchange of oxygen between air that occurs when turbelensi because of the currents. The availability of sufficient oxygen in the water, then the seaweed respiration can take place at night, so the growth will take place optimally. Water mass movement strong enough seaweed capable of keeping clean of sediment so that all parts of thallus can serve to conduct photosynthesis.
The faster the flow, the more water-borne inorganic nutrients and can be absorbed by plants through the process of diffusion. In the standing water plants lack nutrients, thereby disrupting the process of photosynthesis. Thus the sea grass seed should be planted in areas where there are strong currents in the range of 20-40 cm / sec (Sulistijo and Atmadja, 1996). Flow is a mass of water flowing movements that can be caused by wind, sea water density difference and surging tidal propagation length from the open sea (Nontji, 1993).
Dawes (1981) said that ocean currents are caused by a combination of the movement of the wind on the sea surface and the difference in density between different parts of the sea. The movement of waves and currents sometimes strong enough to release the seaweed from the bottom waters. Flow is also one of the causes of reproductive stadia and persporaan seaweed. This is particularly important in the spread of spores, laying and growth.
Winarno (1996) says that the movement of water or currents can move or supply of nutrients from the surrounding waters. Reason seaweed usually grows well in areas with good current movement is if the water is not moving, then the seaweed will take the nutrients available in limited quantities, if available water movement is more active, then the nutrients will be more widely available. Faster currents and the waves are too high can cause crop damage, as can be broken, torn or detached from the substrate. Besides the deployment of nutrients will be hampered and the sea water becomes turbid (Indriani and Sumiarsih, 1999).
According Sulistijo and Atmadja (1996) one of the requirements for determining the location of Eucheuma sp is the flow with a speed of 0.33 to 0.66 m / sec. Meanwhile, according to Ryder (2003) in Iksan (2005) on trial in the lagoon, where the current velocity ranged from 3.6 to 11.6 cm / sec, the growth rate G. parvispora the range of 0.02 to 10.03% per day. The wave height is good for the growth of seaweed that is no more than 30 cm (Apriyana, 2006).